In order to effectively utilize a flammable gas as a fuel or the like, it is necessary to separate air and other gases from a raw gas that includes the flammable gas, and concentrate the flammable gas to an appropriate range. Various devices and methods have been proposed for concentrating such a flammable gas, and in Patent Document 1, for example, a technique is disclosed in which a gas (so-called coal mine gas) occurring in a coal mine that contains methane gas as a flammable gas is used as the raw gas, air (primarily including nitrogen, oxygen, and carbon dioxide) is separated from the raw gas using an adsorbent, and the methane gas is concentrated and utilized.
Specifically, Patent Document 1 proposes a device and method whereby natural zeolite, which is extremely slow to adsorb methane gas compared to nitrogen, is used as the adsorbent (in other words, an adsorbent that adsorbs nitrogen, oxygen, and carbon dioxide with priority with respect to methane gas is used), coal mine gas is introduced to a predetermined pressure through the use of a compressor or the like into an adsorption tower filled with an adsorbent, the oxygen, nitrogen, and carbon dioxide included in the coal mine gas are adsorbed first in the forward part (lower part) of the adsorption tower, the methane gas having a slow adsorption rate is adsorbed in the inner part (upper part) of the adsorption tower, the methane gas is released from the upper part of the adsorption tower until atmospheric pressure is attained, and the methane gas is concentrated.
Air is thereby separated from the coal mine gas as the raw gas using the adsorbent, the methane gas is concentrated, and the concentrated methane gas can be utilized as a fuel or the like.
[Patent Document 1] Japanese Laid-open Patent Application No. 58-198591